This invention relates to a mechanical seal assembly for pumps and the like and more particularly to an improved split mechanical face seal assembly.
Mechanical face seal assemblies are used on a wide variety of machines including pumps and the like having rotating shafts that pass through housings, with the mechanical seal assembly typically being disposed in surrounding relationship to the shaft and cooperating with a stuffing box of the housing to create a sealed relationship between the shaft and housing. Since installation or replacement of mechanical seal assemblies employing one-piece ring members is an extremely time consuming and complex operation, numerous split seal assemblies have been developed to facilitate installation and repair.
The split face seal assemblies are typically split generally diametrically along the axis of the assembly so that the face rings as well as the support rings therefore are all diametrically split so that the various seal assembly components can be mounted on or removed relative to the shaft without requiring excessive disassembly of the overall machine. While split mechanical seal assemblies hence are recognized to possess highly desirable advantages, nevertheless the construction of split seal assemblies continues to present a significant problem with respect to manufacture, assembly and performance thereof.
As to known split mechanical face seal assemblies, most such assemblies have both the stator and rotor face rings split diametrically, and also employ a support collar and a gland member which respectively cooperate with the rotor and stator face rings and which are also diametrically split. All other associated members such as elastomeric seal rings and the like are also split to permit their positioning around the shaft. This construction and the multiple parts thereof hence creates a significant assembly problem since the numerous parts must be field assembled onto the machine (for example a pump), and the parts must cooperate with the precision and fit necessary so as to provide the desired sealing performance. In particular, the split rotor and stator face rings and the respective supporting collar and gland results in a total of eight separate pieces, not counting separate split seals and the like, such that manipulating and assembling this large number of parts at an on-site location and at the same time obtaining or maintaining proper fit and engagement between the parts is thus a relatively complex and time consuming operation. Further, many of the split seals currently commercially available have been unable to provide a consistent performance level since presence of unacceptable leakage levels in such seals has been a fairly common problem.
In addition, because of the difficulties in obtaining proper flatness and opposed flat engagement between the opposed contacting seal faces defined on the diametrically-split rotor and stator face rings, some known constructions have supported these rings and specifically the rotor on resilient support rings in an attempt to compensate for irregularities and distortion. Further, in some of the known constructions the pressure of the working fluid (i.e., the pump fluid) which exists in the stuffing box in surrounding relationship to the seal assembly acts against and urges the rotor face ring more tightly against its supporting collar, and this tends to further increase distortion and the resulting overall performance problems associated with the seal assembly.
Accordingly, it is an object of this invention to provide an improved split mechanical face seal assembly which improves on and overcomes many of the disadvantages which are present in many of the current commercially available split mechanical seals.
More specifically, the present invention relates to an improved split mechanical face seal assembly wherein the stator and rotor face rings and their respective surrounding collar and gland are all split substantially diametrically and are partially factory preassembled to define a reduced number of preassembled subassemblies so as to facilitate shipping, handling and subsequent assembly onto a machine at the job site.
In a preferred embodiment of the invention, the split rotor face ring and the split supportive collar have the cooperating parts thereof subassembled into two subassemblies which define opposed halves for permitting them to be assembled on diametrically opposite sides of a shaft, with each subassembly having the rotor face ring segment carried on the support collar segment, and an elastomeric seal ring which cooperates between the segments being preassembled therebetween. The stator face ring and its supporting gland ring also have the respective split segments thereof, and the other cooperating components such as seal rings and the like, preassembled at the factory to define a pair of subassemblies.
In the improved split mechanical seal assembly of this invention, particularly a preferred embodiment thereof, the split rotor has a rear surface thereof directly and substantially rigidly seated against an opposed surface defined on the split collar, and the rotor and stator face rings have diametrical relationships such that, when externally acted on by the pressurized pump or working fluid, the pressurized fluid exerts an unbalanced force against the rotor which acts in a direction away from the seating surface to thus minimize and in fact possibly reduce the spring-induced seating contact pressure between the rotor face ring and the collar.
Other objects and purposes of the present invention will be apparent to persons familiar with seal assemblies of this general type upon reading the following specification and inspecting the accompanying drawings.